1N5259B_T50R Equivalent & Substitute Parts

Part Overview

The 1N5259B_T50R is a Zener diode rated at 39 V nominal voltage with 500 mW power dissipation and ±5% tolerance. Manufactured by onsemi in DO-35 axial through-hole package, this component is classified as obsolete. Due to its obsolete product status, equivalent substitute parts from active manufacturers are necessary to maintain design continuity and ensure long-term component availability for new production runs and field replacements.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	39	V
Tolerance	±5%	—
Power - Max	500	mW
Impedance (Max)	80	Ohms
Current - Reverse Leakage @ Vr	100 nA @ 30 V	—
Voltage - Forward (Vf) (Max) @ If	1.2	V @ 200 mA
Operating Temperature Range	-65°C to 200°C	—
Mounting Type	Through Hole	—
Package / Case	DO-35 (DO-204AH)	—

Substitute Part Grouping Explanation

Substitution eligibility for the 1N5259B_T50R is determined by the following critical parameters:

Primary Matching Criteria:

Zener voltage: 39 V nominal
Power rating: 500 mW maximum
Package type: DO-35 through-hole axial
Impedance: 80 Ohms maximum
Reverse leakage current: 100 nA @ 30 V

Secondary Compatibility Factors:

Voltage tolerance: ±5% preferred; ±10% acceptable with circuit margin verification
Forward voltage: Maximum 1.5 V @ 200 mA
Operating temperature range: Minimum -65°C to 175°C; 200°C preferred

Substitute parts must maintain identical zener voltage, power dissipation capability, and physical package dimensions. Tolerance variations and forward voltage differences are permissible within the specified ranges, provided the application circuit accommodates these variations without performance degradation.

Parameter Comparison

Parameter	1N5259B_T50R (Main)	1N5259A	1N5259B TR PBFREE
Manufacturer	onsemi	Microchip Technology	Central Semiconductor Corp
Product Status	Obsolete	Active	Active
Voltage - Zener (Nom)	39 V	39 V	39 V
Tolerance	±5%	±10%	±5%
Power - Max	500 mW	500 mW	500 mW
Impedance (Max)	80 Ohms	80 Ohms	80 Ohms
Current - Reverse Leakage @ Vr	100 nA @ 30 V	100 nA @ 29 V	100 nA @ 30 V
Voltage - Forward (Vf) (Max) @ If	1.2 V @ 200 mA	1.5 V @ 200 mA	1.1 V @ 200 mA
Operating Temperature Range	-65°C to 200°C	-65°C to 175°C	-65°C to 200°C
Mounting Type	Through Hole	Through Hole	Through Hole
Package / Case	DO-35 (DO-204AH)	DO-35 (DO-204AH)	DO-35 (DO-204AH)
RoHS Status	Not specified	RoHS non-compliant	ROHS3 Compliant

Engineering Selection Recommendations

1N5259B TR PBFREE (Central Semiconductor Corp)

This part is the primary substitute for the obsolete 1N5259B_T50R. It maintains identical electrical specifications including ±5% tolerance, 39 V zener voltage, 500 mW power rating, and -65°C to 200°C operating temperature range. The forward voltage is superior at 1.1 V versus 1.2 V. This part holds active product status and ROHS3 compliance certification, ensuring long-term availability and regulatory alignment for new designs.

1N5259A (Microchip Technology)

This part is a secondary substitute suitable for applications where tolerance relaxation is acceptable. It maintains the 39 V zener voltage, 500 mW power rating, and DO-35 package compatibility. The ±10% tolerance and maximum forward voltage of 1.5 V represent acceptable deviations for circuits with adequate design margin. Operating temperature range is limited to -65°C to 175°C, which excludes the upper 25°C of the main part's specification. This part is active and available but does not meet ROHS3 compliance.

Frequently Asked Questions (FAQ)

Q: Can the 1N5259A substitute for the 1N5259B_T50R in all applications?

A: The 1N5259A is electrically compatible for most applications. However, the ±10% tolerance versus ±5% tolerance requires circuit verification. Applications requiring precise 39 V regulation within ±5% must account for the wider tolerance band. The reduced upper operating temperature limit of 175°C versus 200°C excludes use in high-temperature environments.

Q: What is the difference between 1N5259B_T50R and 1N5259B TR PBFREE?

A: Both parts share identical electrical specifications: 39 V nominal, ±5% tolerance, 500 mW power, and -65°C to 200°C operating range. The primary differences are manufacturer (onsemi versus Central Semiconductor Corp), product status (obsolete versus active), and compliance certification (ROHS3 for the substitute). The 1N5259B TR PBFREE offers superior forward voltage performance at 1.1 V.

Q: Are all substitute parts in the same DO-35 package?

A: Yes. All listed parts use the DO-35 (DO-204AH) axial through-hole package. Physical dimensions and PCB footprints are identical, permitting direct mechanical substitution without layout modifications.

Q: Which substitute part should be selected for new production designs?

A: The 1N5259B TR PBFREE is the recommended choice for new production. It maintains full electrical equivalence with ±5% tolerance, achieves ROHS3 compliance, and carries active product status ensuring sustained availability.

Q: What is the impact of forward voltage differences between substitute parts?

A: Forward voltage differences (1.1 V to 1.5 V @ 200 mA) affect reverse-biased leakage characteristics and forward conduction behavior. For zener diode applications operating in reverse-bias regulation mode, forward voltage has minimal impact. Applications utilizing forward-bias conduction must verify circuit performance with the specific forward voltage of the selected substitute.

Q: Can the 1N5259A be used in applications requiring the full -65°C to 200°C temperature range?

A: No. The 1N5259A is rated only to 175°C maximum junction temperature. Applications requiring operation at temperatures between 175°C and 200°C must use the 1N5259B TR PBFREE or equivalent parts with 200°C ratings.

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